Abstract: After hot isostatic pressing（HIP） of ZTA 15 alloy, vacuum cycle heat treatment of（920 ℃±10） ℃ for 3 h, and furnace cooling to 250 ℃ was performed in VDF2025 type vertical vacuum heat treatment furnace, and the cycle heat treatment time was 1-5. The effects of vacuum cyclic heat treatment in α+β two-phase region on the microstructure and impact properties at room temperature and 400 ℃ of ZTA15 alloy after HIP were investigated. The fracture morphology was analyzed. The results show that with the increase of cycle time, the grain size increases slightly, the α phase lamella becomes shorter and thicker, and the microstructure gradually changes from Widmanstatten cluster to netted basket structure. The impact absorption energy at room temperature does not change obviously after 1-3 cycles, but it increases significantly after 4-5 cycles. The impact performance at 400 ℃ under different cycles is significantly enhanced than that at HIP condition, and it increases generally with the increase of cycle time. Both at room temperature and 400 ℃, the impact fracture morphologies show tough-brittle mixed fracture characteristics, but the fracture at 400 ℃ has more obvious toughness characteristics.